Question about using a wider taping knife for the first coat

I was watching a guy on a job site in Tacoma finish a big ceiling. He used a 10 inch knife for the first coat on the flat seams. I always stuck with a 6 inch for that step. He told me, 'A wider blade spreads the mud thinner and flatter, less sanding later.' I tried it yesterday on a garage project. It felt weird at first, but after a few seams I got the hang of it. The mud went on smoother and I could see fewer ridges right away. It did take a bit more pressure to keep it flat. Has anyone else made this switch and found it saves time on the sanding stage?

3 comments

3 Comments

craig.viola1d ago

Honestly, it's just mud on a seam. I get the logic, but a 6 inch knife has never failed me. The extra pressure with a 10 inch feels like more work right then, so where's the real time save? If your first coat is that lumpy you're fighting it later, maybe the mix is off or you're loading too much mud. I've seen guys make perfect seams with a putty knife. It's not the tool, it's the hand holding it.

davis.olivia1d ago

Yeah but what about the arm fatigue over a whole day? A six inch means more passes, more wrist movement. My elbow's shot from years of that, switching to a ten inch let me use my shoulder more, spread the work out. It's not about one seam, it's about the five hundredth one.

ward.anna1d ago

Exactly, it's about the five hundredth one. Craig.Viola is right that a good hand can use any tool, but that's missing the point. A ten inch knife forces you into better, bigger movements from the start, so you're not wrecking your joints with tiny, repeated flicks. You adapt to the tool. Starting with a six inch builds bad habits that catch up to you, like Olivia said. The real skill is learning to let the longer knife do the work so you're not fighting it.